Concentrations of four trace elements (Cd, Ni, Cu and Pb) were determined in eggshells of grey heron (Ardea cinerea) and black-crowned night herons (Nycticorax nycticorax) from Nallihan Bird Paradise, which is located in the northern part of Sariyar Dam Reservoir, Turkey. Results indicated that, within the same area, these ardeid species differed in the levels of Cd, Cu and Pb in their eggshells (generally grey heron > night heron), possibly because females may have foraged in different habitats and regions. Geometric means found for Cd, Ni, Cu and Pb in eggshells were 0.931 mg/kg, 0.405 mg/kg, 6.755 mg/kg and 4.567 mg/kg, respectively, for grey heron; and 0.230 mg/kg, 0.220 mg/kg, 1.369 mg/kg and 1.108 mg/kg, respectively, for night heron. High bioaccumulation from sediments to eggshells occured for Cu and Pb, while Cd and Ni exhibited low accumulation. Bioaccumulation ratios were calculated as 19.63 (Cu) and 22.9 (Pb) in eggshells of grey herons. In conclusion, eggshells of grey herons appeared to be good bioindicators for monitoring of Cu and Pb in Nallihan Bird Paradise.